I'm not a pro and have not worked professionally since the very early 1990s. I don't mind a fine cleaning wisp, if you use (as I do) lenses from 80 to 100+ years old you have to live with minor marks most of the time.
Originally Posted by vpwphoto
I have a 9 1/2" Dagor in a good early Compound which I picked up at a show. It has a 9mm scratch - almost a gouge - right in the center of the rear outer element - the worst possible location. I painted the blemish black, and the lens is just fine. I have another of the same vintage and focal length to compare it with and can find no effect. I don't think I did paying work with this lens, but I wouldn't hesitate to.
The front element of my 105 Nikkor has some light abrasions, which so far have caused no trouble - but I'm fairly fanatical about using proper lens hoods on all my lenses whether they are coated or not.